As the body pigment for cosmetic products, spherical silica and spherical polymers comprised of nylon, polyethylene, and polymethacrylate are known and being used. However, there is still a need for a powder having good slipping property (spreadability) and adhesive property to the skin. Moreover, there is a case in which the body pigment is required to have a function of exhibiting anti-slipping property after exhibiting a certain level of slipping property. And, as a matter of course, the body pigment must be capable of absorbing sebaceous component as its basic prerequisite. In recent years, body pigments intended for improving spreadability have been disclosed such as, for example, agglomerated pigment particles (JP-A-2001-22031S, JP-A-2001-247790, etc.) which are combined with a moisturizer or various organic matters and are given a crumbling property.
However, these body pigments do not have sufficient adhesiveness, though they have a good slipping property to the skin. Also, when considering the uses in all types of cosmetics, their application area may be limited depending on the kinds of the binders because they are a randomly agglomerated body which is previously combined by the bonding action of a moisturizer. Therefore, there is need for a body pigment which has good slipping property and adhesive property and also provides versatility of application without being limited by the type of the binder.
Magnesium hydroxide and basic magnesium carbonate are known as a flame retarding additive (hereinafter referred to ‘flame retardant’) which is incorporated in a resin component and paper (for example, JP-A-H3-197316, JP-A-H3-197314). Most of these flame retardants make use of the endothermic reaction through which these compounds change into oxides. To maximize the flame retardant effect in the course of these changes, a shape factor of the pigment plays an important role, i.e., a pigment with a large surface area per unit volume is desirable.
A process for preparing magnesium hydroxide is disclosed in which magnesium oxide is added to the slurry of magnesium hydroxide to form spherical or scaly leaf like fine particles through hydration, and then these particles are deposited on the surface of secondary particles of the magnesium hydroxide (JP-A-2001-158617). This process includes generation of secondary particles of magnesium hydroxide and succeeding hydration treatment on the surface of the secondary particles by adding magnesium oxide particles. Thus, this process relates to a highly concentrated surface treatment of water slurry to improve its transport efficiency. In other words, the process is to provide a pigment with a dual structure consisting of a secondary particle at the center and other particles on its surface through a two-step processing. And because of the nonuniform stepped surface structure, the particle lacks smooth slipping property and therefore is not desirable for use in cosmetic body pigments.
Moreover, as an example of readily crumbling soft agglomerated powders, an agglomerated powder, of which the primary particle is coated with solid type organic matter and liquid oil, is disclosed which has both a good slipping property and an anti-slipping property (JP-A-9-31158). In this powder, since the coating material is limited to organic materials and a liquid oil is used therewith, its application to cosmetics may be limited depending on the kind of the liquid oil. Also, this powder is not preferable in that due to the agglomerated particle structure, it has low adhesive property between particles and would be easily exfoliated when used in real cosmetic products.